Children with Attention-Deficit/Hyperactivity Disorder (ADHD) participated in double-blind placebo-controlled randomized trails of stimulants while undergoing anatomic imaging with magnetic resonance imaging (MRI). The four approached are (1) anatomic imaging with magnetic resonance imaging, (2) neuropharmacology, (3) genetic studies, and (4) neurophysiological investigations. In anatomic studies, girls with ADHD have shown similar basal ganglia and prefrontal brain abnormalities to those seen in our previous study of boys. Subjects also participate in a longitudinal study of brain development. An on going placebo-controlled study compares a recently marketed preparation of mixed amphetamines salts to the standard amphetamine formulation and a newly formulated sustained release preparation. These subjects and others also participate in studies of the genetics of ADHD using family association and affected-sibling designs in collaboration with a multi- center multi-institute consortium. Results from our own samples do not support previously reported abnormalities in the D4 dopamine receptor or in the dopamine transporter. Neurophysiological approaches have investigated the usefulness of eye movement tasks in ADHD. Girls with ADHD show executive function abonormalities on Delayed Response and Go- No Go eye movement tasks, but substantial practice effects may limit task utility. Single- and paired-pulse transcranial magnetic stimulation are being used to probe the motor system in ADHD and matched controls in a collaborative study. - Children and Adolescents, ADHD, MRI, Genetics, methylphenidate, dextroamphetamine, Adderall - Human Subjects & Human Subjects: Interview, Questionaires, or Surveys Only